1. Field of the Invention
The present invention relates generally to a wire saw control method and a wire saw for slicing a workpiece such as silicon, glass and ceramics, into a number of wafers.
2. Description of Related Art
A wire saw forms a wire row by winding a wire on a plurality of grooved rollers, and runs the wire at a high speed and presses a workpiece against the wire row to thereby slice the workpiece into wafers. When the wire saw slices a column-shaped workpiece, the slicing length varies according to the slicing positions such as a slicing start position, a slicing end position and a slicing intermediate position. This changes the cutting resistance to the wire and the wire deflection (a wire displacement in a workpiece feeding direction). The change in the wire deflection causes the wire to run unstably and deteriorates the workpiece slicing accuracy.
To address this problem, a conventional wire saw estimates the cutting resistance according to the workpiece slicing position, and controls a workpiece feed speed according to the estimated cutting resistance, thus preventing a change in the wire deflection.
The cutting resistance, however, varies according to a variety of conditions such as the shape of the workpiece and the workpiece feed speed, and thus, it is difficult to correctly estimate the cutting resistance. For this reason, the conventional wire saw cannot slice the workpiece accurately.